As the technology is improved, more and more functions and protection mechanisms are integrated in a controller of power converter, such as over-voltage protection, under-voltage protection, constant output power control, and constant voltage-second control, etc. However, adding these functions and protection mechanisms usually requires an increase in the number of pins on the controller chip of the power converter, thereby increasing the elements and cost. In order to decrease the pin count, there was proposed a concept of multi-function pin, i.e., utilizing a pin to provide a variety of functions. For example, U.S. Pat. No. 6,643,153 to Balakrishnan et al. disclosed a method and apparatus providing a multi-function terminal for a power supply controller. However, the implementation of these functions and protections always requires input information or output information of the power converter. For instance, for a power converter, input over-voltage protection requires detection on the input voltage of the power converter, and output over-voltage protection requires detection on the output voltage of the power converter. Unfortunately, a conventional multi-function pin can only obtain either input information or output information, and thus can only implement those functions or protections that use either input information or output information.
Thus, it is desired an apparatus and method capable of obtaining both input information and output information of a power converter so as to implement multiple functions or protections for the power converter.